The influence of dietary protein level on cholesterol metabolism in the chicken was investigated. The rate of hepatic cholesterol synthesis was positively related to the dietary protein level while an increase in dietary protein resulted in a decrease in plasma cholesterol levels. Increasing dietary protein resulted in a more rapid removal of cholesterol from the blood and excretion in the feces as cholesterol and bile acids. The estimated contribution of skin to total fatty acid synthesis in the intact chicken was about 7 percent, while skin accounted for approximately 6 percent of total cholesterol synthesis. Examination of the effect of dietary lipid on lipogenesis in the rat indicated that dietary medium-chain triglycerides were much less effective than dietary corn oil in depressing fatty acid synthesis and lipogenic enzyme activity in rat adipose tissue. The relative importance of the liver was increased when dietary fructose, rather than dietary glucose, was fed to rats; however, the total capacity of the animal to synthesize fatty acids was unchanged. A hyperlipogenic state was produced in both pigs and mice by restricting the time in which the animals had access to food.